How To Test The TP Sensor (1998-2001 1.3L Swift / Chevy Metro)

How To Test The Throttle Position Sensor -TPS- (1998, 1999, 2000, 2001 1.3L Suzuki Swift / Chevy Metro)

The throttle position sensor (TPS) on your 1998-2001 1.3L Suzuki Swift (Chevy Metro) can be easily and accurately tested with a simple multimeter.

No scan tool is required to test the TP sensor (to see if it's bad or not). In this tutorial I'll show you just how in a step-by-step way.

To see the TP sensor's wiring diagram go to: 1998-2001 TP Sensor Circuit Diagram (1.3L Swift / Metro).

Symptoms Of A Bad Throttle Position Sensor

Your Suzuki Swift's Powertrain Control Module (PCM) uses the throttle position sensor to find out how much you have stepped on (or off) the accelerator pedal.

Because the info that the TPS provides is such a critical part of the PCM's fuel injection strategy, when the throttle position sensor (TPS) fails your Suzuki Swift (Chevy Metro) is gonna' resent it and will let you know something is wrong. You'll see one or more of the following symptoms:

  1. Check engine light (CEL) shining nice and bright.
  2. Diagnostic trouble codes (DTC) stored in the PCM's memory:
    • P0121: Throttle Position Sensor Performance.
    • P0122: Throttle Position Sensor Voltage Low.
    • P0123: Throttle Position Sensor Voltage High.
  3. Your Suzuki Swift (Chevy Metro) fails the state mandated emissions test.
  4. Bad gas mileage.
  5. Hard start and/or extended cranking time (after shut off).
  6. Black smoke coming out of the tailpipe.
  7. Hesitation when accelerating your vehicle down the road.

Where To Buy Your TP Sensor And Save

Where can you buy the TP sensor for your Suzuki Swift (Chevy Metro)? You can buy it at your local auto parts store but it's gonna' cost a whole lot more. I suggest taking a look at the price of the TP sensor in the following links and compare:

Not sure if the above TP sensor fits your particular Suzuki Swift (Chevy Metro)? Don't worry, once you get to the site, they'll make sure it fits by asking you the particulars of your vehicle. If it doesn't fit, they'll find you the right one.

TEST 1: Testing The Throttle Position Sensor Voltage Signal

To find out if the TPS is bad (or not), we're gonna' tap into the LT GRN/WHT (light green w/ white stripe) wire of the sensor's 3-wire connector with a multimeter.

In case you're wondering, the LT GRN/WHT wire is the one that carries the throttle angle voltage signal (the TPS creates) to the PCM.

In a good and working TPS, the voltage signal at closed throttle is about 0.2 to 0.9 Volts DC. As you open the throttle, this voltage should increase to about 4.5 to 4.8 Volts DC.

If the TPS is bad, the voltage usually stays stuck in one value no matter how much you open the throttle plate or the voltage skips or goes erratic (as you open the throttle plate).

NOTE: This test is done with the key on but engine off (KOEO) and while the TP sensor remains connected to its electrical connector.

OK, let's start:

  1. 1

    Place your multimeter in Volts DC mode.

  2. 2

    Connect the red multimeter test lead to the LT GRN/WHT wire of the sensor's connector. This is the circuit that supplies the TP Signal to the PCM.

    If you don't have a multimeter or need to upgrade yours, check out my recommendation: Buying A Digital Multimeter For Automotive Diagnostic Testing (found at:

    NOTE: The throttle position sensor has to remain connected to its connector for this test to work (this is where a wire piercing probe comes in handy to get to the signal inside the wire. To see what one looks like, click here: Wire Piercing Probe Tool.)

  3. 3

    Connect the black multimeter test lead to the battery negative (-) terminal.

  4. 4

    Have your helper turn the key to the ON position, but don't start the engine (this will power up the TP sensor).

  5. 5

    Your multimeter should report a voltage between 0.2 to 0.9 Volts DC. If your multimeter doesn't, don't worry about it just yet, continue with the other steps.

Part 2

  1. 6

    Slowly open the throttle plate (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.

    For this test result to be accurate, you need to open the throttle plate by hand and not from inside the vehicle.

  2. 7

    As the throttle plate opens, the voltage numbers will increase.

    This increase in voltage should be smooth and without any gaps or skips.

    Once the throttle plate is wide open, your multimeter should read somewhere between 3.5 to 4.5 Volts DC.

  3. 8

    Now, slowly close the throttle plate.

    As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 4.

Part 3

  1. 9

    Lightly tap on the throttle position sensor with the handle of a screw-driver (or something similar, and I want to emphasize the words ‘lightly tap’) as you slowly open and close the throttle plate and observe the multimeter.

    If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers.

  2. 10

    Repeat step 9 several times to make sure of your multimeter test results.

Let's take a look at your test results:

CASE 1: The multimeter showed the voltage value increase then decrease as you opened/closed the throttle plate. This test result confirms that the TP sensor is OK and not defective.

CASE 2: The voltage value DID NOT increase or decrease as you opened/closed the throttle plate. This tells you that the TP sensor is bad and needs to be replaced.

If I where in your shoes, I would still make sure that the TP sensor is getting both power and Ground. To check for power on the LT GRN wire, go to: TEST 2: Verifying Throttle Position Sensor Has Power.

CASE 3: The multimeter DID NOT register any voltage. This test result doesn't condemn the TP sensor as bad just yet.

Why? Because the TP sensor may be missing either power or Ground. So the next step is to check that the TP sensor is getting power, go to: TEST 2: Verifying Throttle Position Sensor Has Power.